Right middle cerebral artery ligation in the rat lead to reductions in catecholamine concentrations of approximately 30 to 50% in the cortex, locus coeruleus, substantia nigra and A10 cell groups with a partial or complete recovery within 4 to 5 weeks. In addition, right hemispheric infarction leads to a period of hyperactivity lasting about three weeks. Left middle cerebral artery ligation, although the procedure is identical and the lesion appears to be comparable to right sided infarcts, does not lead to any substantial reductions in catecholamines or any disturbance of spontaneous activity. The focus of this study is to evaluate whether these asymmetries can be elicited by specific lesions of catecholaminergic terminals in the cortex or by lesions of intrinsic cortical neurons. In addition, the specificity of vascular lesions within the distribution of the middle cerebral artery will be evaluated by comparing the effects of suction lesions with infarcts. There are 4 specific objectives outlined: 1) compare the effects of suction lesions in the distribution of the middle cerebral artery and at other locations with the effects of cerebral infarction using a high pressure liquid chromatograph to measure NE and DA concentrations in the cortex and brainstem and daily running wheel and open field activity as well as several other "emotional behaviors" to test the behavioral state of the animal. 2) Inject the catecholamine neurotoxin 6-hydroxydopamine into the cerebral cortex in the area of the middle cerebral artery and other brain areas and measure catecholamines and behaviors using the same methods as aim 1. 3) Inject kainic acid into the cerebral cortex in an effort to lesion only intrinsic neurons without injuring neurons of passage such as the catecholaminergic neurons and measure catecholamines and behavior using the same methods as no 1 and 2. 4) Lesion specific subcortical cell bodies which contain catecholamine and evaluate the effect of cerebral infarction with these pathways removed. The biochemical and behavioral effects will be measured using the methods as the previous aims.